Static electricity has a tendency to build up within and on the surface of fabrics during use. Buildup of static electricity is a nuisance in garment handling and to the wearer and may also pose a hazard to the wearer in certain environments, and in particular in flammable gas environments. As a result, it is desirable for fabrics to prevent or minimize static electricity build up.
It has been known to incorporate antistatic filament yarns into fabrics to satisfy one or more standards for static electricity in apparel, including EN 1149 (Electrostatic properties of protective clothing) and MIL-C-83429B (Military specification: cloth, plain and basket weave, aramid) (as tested in accordance with FTMS 191A Test Method 5931). One known antistatic filament yarn is available from Barnet under the trade name Nega-Stat®. The antistatic filament yarn is a conductive yarn, which dissipates (or prevents the buildup of) static electricity by conducting the electric charge along the filament yarns to a ground (such as the body of a user). The antistatic filament yarn has been incorporated into fabrics in a continuous grid pattern to facilitate conduction of static electricity through the garment. While such constructions effectively dissipate static electricity in the fabric, the filament yarn is expensive and results in a high fabric cost.
Another known method for minimizing or preventing static electricity build up in a fabric is to form a fabric from spun yarns (rather than filament) and incorporate approximately 2% or more antistatic staple fibers into the spun yarns used in the fabric. In this manner, the antistatic staple fibers (such as 401-ECS staple fibers, available from Ascend Performance Materials under the No-Shock® line of products) are more or less evenly distributed throughout the entire fabric. 401-ECS staple fibers have a carbon-based antistatic component. It will be recognized that in such constructions, the antistatic fibers are not continuous and thus will not conduct electricity through the fabric; rather, the antistatic fibers dispersed throughout the fabric dissipate the static electricity that builds up by way of an inductive field.
Antistatic fibers are relatively dark as compared to typical staple fibers used in fabric constructions. As a result, the appearance of fabrics having antistatic staple fibers dispersed throughout the fabric is undesirable when light shades of fabric are desired, and in particular when it is desirable for the fabric to satisfy standards for high visibility apparel. It may not be possible, for example, to satisfy ANSI 107 (High-Visibility Safety Apparel and Headwear) when using a fabric having the relatively darker antistatic staple fibers dispersed throughout. A similar problem can occur when trying to form a fabric from dark shades, as the antistatic fibers, while darker than light shade fibers, are not as dark as commonly used dark shade fibers and will thus appear lighter against the dark background of the other staple fibers. Neither result is desirable. Visual appearance problems can also occur when using conductive antistatic filament yarns in a grid pattern due to voids or variation in the appearance of the filament in the pattern.